Field of the Invention
The invention relates to a continuous casting mold of the kind comprising an interior section and an outer jacket section.
A continuous casting mold of this kind is known from German No. AS 19 64 048. In this mold the interior section is defined by plates which enclose a hollow mold space and which are provided on the outside with grooves formed by milling. The external walls of these interior sections are covered by a jacket section which in this case is formed by supporting plates which close up the said grooves. Cooling water is passed through these grooves so that sufficient heat can be extracted from the melt in the continuous casting process, particularly when steel is being cast. Correspondingly the molten metal will solidify and emerge from the lower part of the mold with an adequately firm and supportive outer shell. In addition to this type of split, or divided continuous casting mold (which is particularly well suited for the continuous casting of slabs), there are also undivided continuous casting molds with smaller casting cross sections for casting billets and blooms. Such undivided continuous casting molds also receive external machining to form grooves to which the coolant, which is generally water, can be applied. It is also possible to drill cooling channels into the mold walls. However this is relatively difficult because of the need to maintain a precise drilling position in view of the subsequent connections. Milled groove passages and drilled bores have this in common that the workpiece, generally a copper casting, must be subjected to chip removing machining processes. In such work the possibility cannot be excluded that unintentional material separation zones may be broached into which the coolant would then be able to enter. Such uncontrolled spread of cooling water inside the mold wall will, as a rule, render the latter useless. A further chip removing treatment is applied to the inside walls of the molds in order to make them sufficiently smooth and dimensionally accurate for the pass of the casting. Here again one cannot rule out the risk of cutting into pores created by the original casting process or other cavities in the walls. In such a case the mold is also quite useless. Added to this it must be remembered that the service life of the mold is limited by erosions which start from the inside wall. It is true that the latter may be compensated to a limited extent by further chip removing machining but this means, at any rate, that the mold in question is taken out of production for a corresponding length of time which, in turn, requires expensive stock holdings. Mechanical reconditioning of the molds is severely limited on the one hand by the dimensional specification of the continuous casting which must be observed and, on the other hand, by the required minimum wall thicknesses of the molds. This means that wall thickness in particular is considerably restricted due to the provision of such cooling channels or bores. With insufficient outer support such thin-walled molds may tear all the more easily as their mechanical strength at right angles to the radial grain orientation which is preferred due to the casting of the molds generally coincides with the direction of heat flow.